(a) Field of the Invention
The present invention relates to thin film transistor array panels for a liquid crystal display and the methods for manufacturing the same.
(b) Description of the Related Art
A liquid crystal display (LCD) is one of the most popular flat panel displays (FPDs). The liquid crystal display has two panels having electrodes for generating electric fields and a liquid crystal layer interposed therebetween.
The transmittance of incident light is controlled by realigning the liquid crystal molecules of the LCD, as the intensity of the electric field applied to the liquid crystal layer changes.
In the most widely used liquid crystal display, the field-generating electrodes are provided at both panels, with one of the panels having switching elements such as thin film transistors and pixel electrodes, and the other panel having color filters and black matrix.
In general, a thin film transistor array panel is manufactured by a photolithography process using photoresist pattern as an etch mask. However, the misalignment of interlayes in fabricating a multi-layered structure negatively affects display characteristics of the LCD. To solve this problem, it is desirable that an alignment key of an opaque material is formed of the same layer as the lowest layer of the thin film patterns.
On the other hand, it is important to increase an aperture ratio of the thin film transistor panels of LCD to improve a brightness of LCD. However, the LCD has several obstacles in reducing the aperture ratio of the thin film transistor. Firstly, a certain distance between the pixel electrode and the data line must be maintained in order to avoid the parasitic capacitance generated therebetween by coupling effects. Secondly, a black matrix must be wide enough to cover a possible misalignment of the two panels. To solve these problems, several methods have been suggested. One suggests an insulating layer interposed between the pixel electrode and the data line and made of organic material having a low dielectric constant. The other suggests color filters formed on the same panel having thin film transistors.
However, the latter case is economically unsound. Because the color filters are formed after more expensive processes of forming thin film transistor, the failure in the color filter formation process wastes a lot of resources and increases the manufacturing costs. On the other hand, the former method cannot generate enough storage capacitance between the gate line and the pixel electrode.